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Energy systems in cost-optimized design of nearly zero-energy buildings
No full textCost optimization is one of the key elements of the EU regulatory framework concerning the energy performance of buildings. From this economic point of view, the optimum occurs when the global cost over the lifecycle of a building is minimized, and the cost-optimal energy performance level is that related to the minimum global cost. To determine this cost-optimal level by evaluating a great number of design alternatives, it is necessary to exploit automated optimization search procedures. The work presented here concerns the application of cost-optimal methodology, as defined by European regulation, to a low-consumption single-family house in France. The calculation is performed through an iterative input-output process in a computing environment that combines TRNSYS®, transient system simulation tool, with GenOpt®, generic optimization program. The methodology that was adopted allowed around ten thousand building configurations to be simulated in a reasonable computational time. The paper focuses on how the energy system affects the technical and economic optimal design solutions of the building in two different French climate condition
SIERRA—Simulation environment for memory redundancy algorithms
No full textExtreme-scale computer systems take advantage of large arrays of general-purpose multicore processors coupled with specialized manycore accelerators. In order to support complex applications and correctly feed such processing elements, increasingly larger memory cores are integrated at different levels of the hierarchy. However, the adoption of increasingly aggressive manufacturing processes makes the memory sub-system particularly sensitive to faults. Error correcting codes (ECCs) allow the memory to recover from faults at run-time without interfering with the application execution. However, due to the loss of performance introduced every time an error must be corrected, the persistence of faults requires a more radical repair approach in which faulty cells are physically replaced by spare ones. Memory redundancy analysis (MRA) algorithms are used to drive the allocation process of spare resources. Many one-dimensional and two-dimensional MRAs have been proposed, but tools for evaluating their recovering capability are still not well established. This paper presents SIERRA, a simulation environment for precisely evaluating the repair efficiency of an MRA considering different fault signatures and faulty memory configurations. Our simulation engine provides a precise estimation of the MRA quality by analyzing the behavior of the MRA on several faulty memory configurations. To this end, different parameters such as the area of the memory blocks and the defect density are taken into account. The evaluation of the quality of an MRA takes into account its repairing capability, the power consumption derived from its execution, and the area overhead. Thanks to the use of a database for storing information, our tool is able to speed-up the simulation process by distributing it among several nodes. All these features make SIERRA essential in supporting the design of next-generation high-performance computers
Human powered press for producing straw bales for use in construction during post-emergency conditions
No full textThe straw bale construction technique is considered one of the most appropriate for the improvement of housing conditions in developing countries and for the reconstruction in post-emergency situations. In this environment, no electricity or other energy sources are available; for this reason, straw bales have to be produced by means of a human powered press. This paper presents the designing process of a manual press, that is a key tool for the objectives introduced above. Following definition of the machine architecture and the actuating mechanism (slider-crank), a design method based on energy considerations is introduced. Given the mechanical properties of straw, described by a simplified linear model, and the maximum work that a human operator can do, applying the designing method, it was possible to obtain the main functional parameters of the machine, such as the pressing piston stroke, and the length both of the connecting rod and of the crank. The method was experimentally validated and a prototype assembled and used for the production of infill bales in the construction of a warehouse in Hait
Interpretation and generalization of complexity pursuit for the blind separation of modal contributions
No full textComplexity pursuit (CP) has recently been proposed as an elegant and simple solution to blindly (i.e. without measuring the inputs) separate the modal contributions in the vibration responses of a structure. This potentially finds considerable interest in operational modal analysis and related applications. This paper analyses the theoretical ins and outs of the method. It also revises its physical interpretation in the modal analysis context. CP is found to separate components which are the least dispersive (i.e. invariant under linear filtering), a property that well characterizes the modal responses of lightly damped systems. However, it is also found to suffer from the same limitations as other blind source separation methods used in the state-of-the-art, namely the difficulty to separate strongly coupled modes and to identify complex mode shapes. Finally a generalization of CP is proposed which intends to widen its applicability. Interestingly, the generalized CP happens to include the well-known SOBI algorithm as a particular cas
Analysis of two heat storage integrations for an Organic Rankine Cycle Parabolic trough solar power plant
No full textAmong the concentrated solar power technologies, those based on Organic Rankine Cycles have a very low market presence. However they have favorable characteristics for applications with low temperature and small/medium size (<10 MW), such as off-grid applications or distributed power generation. In this paper is analyzed a 5MW parabolic trough plant integrated with an Organic Rankine cycle power block and thermal storage. On this purpose, two different thermal storage integrations are analyzed. They are based on two different heat storage layouts: direct system using Hitec XL both as Heat Transfer Fluid and as storage medium; indirect system using Therminol VP-1 as Heat Transfer Fluid and Hitec XL as storage medium. Full system performance at rated and off-design conditions is presented operating with different organic working fluids. Its potential application and main challenges for its development are discussed in terms of performance and costs. Among the analyzed working fluids, the best results were obtained for the cycle working with Toluene with an efficiency at the power block of 31.5% and an estimated power block cost of 825 €/kW. The indirect storage layout was the most interesting from the point of view of Levelized Electricity Cost (16.19 c€/kW) and productivity (28.2 GW h/y for a 5 MWel plant) for 10 h of storage However, it results in a storage tanks volume 26% greater than the obtained for the equivalent direct storage layout. The results show the competitiveness and the potential of the proposed integrated small size parabolic trough designs for isolated applications as mines or for some distributed generation uses where grid capacity is limited
Single-Frequency Receivers as Permanent Stations in GNSS Networks: Precision and Accuracy of Positioning in Mixed Networks
No full textContinuous Operating Reference Stations (CORSs) are widely used for many purposes including precise positioning, mapping and monitoring. These architectures are composed of a control centre and a number of permanent stations consisting of geodetic antennas and dual frequency receivers. This infrastructure is costly due to the instruments used and has the additional disadvantage in that inter-station distances between CORSs, that are often too high if a single-frequency receiver acts as a rover. This study focuses on the usefulness of permanent single-frequency stations in order to increase density of existing CORSs for monitoring purposes. In this connection, some innovative GNSS networks composed of geodetic and mass-market L1 receivers have been developed and tested, analyzing the performance of rover positioning in terms of quality, accuracy and reliability in real time. Some tests have been carried out considering different types of receivers (geodetic and mass market) and antennas (patch and geodetic), in real-time mode. The results obtained show that with a "classical" network (where the mean inter-station distances between CORSs are about 40 km) an accuracy of about 5 cm can be achieved after fixing the phase ambiguity with a mass-market L1 receiver acting as rover. In addition, the Time-To-Fix period is very short, being less than 2 min. Despite the obvious fact that increased inter-station distance leads to reduced accuracy, the degree of precision obtainable remains useful for many applications, such as mobile mapping and traffic control. In short, the experiments under examination performed with low-cost GNSS receivers will be useful for many types of applications (landslide monitoring, traffic control), especially where the inter-station distances of permanent GNSS stations are around 40 km
Colloidal behavior of goethite nanoparticles modified with humic acid and implications for aquifer reclamation
No full textNanosized colloids of iron oxide adsorb heavy metals, enhance the biodegradation of contaminants, and represent a promising technology to clean-up contaminated aquifers. Goethite particles for aquifer reclamation were recently synthesized with a coating of humic acids to reduce aggregation. This study investigates the stability and the mobility in porous media of this material as a function of aqueous chemistry and it identifies the best practices to maximize the efficacy of the related remediation. Humic acid-coated nano-goethite (hydrodynamic diameter ~90 nm) displays high stability in solutions of NaCl, consistent with effective electrosteric stabilization. However, particle aggregation is fast when calcium is present, and to a lesser extent also in the presence of magnesium. This result is rationalized with complexation phenomena related to the interaction of divalent cations with humic acid, inducing rapid flocculation and sedimentation of the suspensions. The calcium dose, i.e., the amount of calcium ions with respect to solids in the dispersion, is the parameter governing stability. Therefore, more concentrated slurries may be more stable and mobile in the subsurface than dispersions of low particle concentration. Particle concentration during field injection should be thus chosen based on concentration and proportion of divalent cations in groundwater
Cellular Network Traces Towards 5G: Usage, Analysis and Generation
No full textDeployment and demand traces are a crucial tool to study today's LTE systems, as well as their evolution toward 5G. In this paper, we use a set of real-world, crowdsourced traces, coming from the WeFi and OpenSignal apps, to investigate how present-day networks are deployed, and the load they serve. Given this information, we present a way to generate {\em synthetic} deployment and demand profiles, retaining the same features of their real-world counterparts. We further discuss a methodology using traces (both real-world and synthetic) to assess (i) to which extent the current deployment is adequate to the current {\em and future} demand, and (ii) the effectiveness of the existing strategies to improve network capacity. Applying our methodology to real-world traces, we find that present-day LTE deployments consist of multiple, entangled, medium- to large-sized cells. Furthermore, although today's LTE networks are overprovisioned when compared to the present traffic demand, they will need substantial capacity improvements in order to face the load increase foreacasted between now and 2020
Infinite S-expansion with ideal subtraction and some applications
No full textAccording to the literature, the S-expansion procedure involving a finite semigroup is valid no matter what the structure of the original Lie (super)algebra is; however, when something about the structure of the starting (super)algebra is known and when certain particular conditions are met, the S-expansion method (with its features of resonance and reduction) is able not only to lead to several kinds of expanded (super)algebras but also to reproduce the effects of the standard as well as the generalized Inönü-Wigner contraction. In the present paper, we propose a new prescription for S-expansion, involving an infinite abelian semigroup S^(∞) and the subtraction of an infinite ideal subalgebra. We show that the subtraction of the infinite ideal subalgebra corresponds to a reduction. Our approach is a generalization of the finite S-expansion procedure presented in the literature, and it offers an alternative view of the generalized Inönü-Wigner contraction. We then show how to write the invariant tensors of the target (super)algebras in terms of those of the starting ones in the infinite S-expansion context presented in this work. We also give some interesting examples of application on algebras and superalgebras